[DUX-1511] Add the ability to track warnings through re-compilation

Closes #148

Author: jkeuhlen

docs/cli.md

@@ -89,6 +89,13 @@ Don't interrupt reloads when files change.
 
 Depending on your workflow, `ghciwatch` may feel more responsive with this set.
 
+</dd>
+<dt><a id="--track-warnings" href="#--track-warnings"><code>--track-warnings</code></a></dt><dd>
+
+Track warnings across recompilations.
+
+When enabled, warnings will be preserved in memory even when files are recompiled due to dependency changes, helping prevent "ephemeral warnings" from being missed.
+
 </dd>
 <dt><a id="--completions" href="#--completions"><code>--completions &lt;COMPLETIONS&gt;</code></a></dt><dd>
 

src/cli.rs

@@ -83,6 +83,13 @@ pub struct Opts {
     #[arg(long, hide = true)]
     pub tui: bool,
 
+    /// Track warnings across recompilations.
+    ///
+    /// When enabled, warnings will be preserved in memory even when files are recompiled
+    /// due to dependency changes, helping prevent "ephemeral warnings" from being missed.
+    #[arg(long, env = "GHCIWATCH_TRACK_WARNINGS")]
+    pub track_warnings: bool,
+
     /// Generate Markdown CLI documentation.
     #[cfg(feature = "clap-markdown")]
     #[arg(long, hide = true)]

src/ghci/compilation_log.rs

@@ -1,5 +1,6 @@
 use crate::ghci::parse::CompilationResult;
 use crate::ghci::parse::CompilationSummary;
+use crate::ghci::parse::CompilingModule;
 use crate::ghci::parse::GhcDiagnostic;
 use crate::ghci::parse::GhcMessage;
 use crate::ghci::parse::Severity;
@@ -9,6 +10,7 @@ use crate::ghci::parse::Severity;
 pub struct CompilationLog {
     pub summary: Option<CompilationSummary>,
     pub diagnostics: Vec<GhcDiagnostic>,
+    pub compiled_modules: Vec<CompilingModule>,
 }
 
 impl CompilationLog {
@@ -31,6 +33,7 @@ impl Extend<GhcMessage> for CompilationLog {
                         reason = progress.reason.as_deref().unwrap_or(""),
                         "Compiling",
                     );
+                    self.compiled_modules.push(progress.module);
                 }
                 GhcMessage::Diagnostic(diagnostic) => {
                     if let GhcDiagnostic {

src/ghci/error_log.rs

@@ -1,3 +1,4 @@
+use camino::Utf8Path;
 use camino::Utf8PathBuf;
 use miette::IntoDiagnostic;
 use tokio::fs::File;
@@ -23,6 +24,11 @@ impl ErrorLog {
         Self { path }
     }
 
+    /// Get the path for this error log writer, if any.
+    pub fn path(&self) -> Option<&Utf8Path> {
+        self.path.as_deref()
+    }
+
     /// Write the error log, if any, with the given compilation summary and diagnostic messages.
     #[instrument(skip(self, log), name = "error_log_write", level = "debug")]
     pub async fn write(&mut self, log: &CompilationLog) -> miette::Result<()> {